The U.S. Pat. Nos. 3,757,705; 5,390,803; 4,656,952; 5,676,263; 4,852,501; 4,595,107; and the U.S. Pat. Ser. No. 09/305,081 disclose a rack comprising a plurality of tapered tubes and locating pieces, which are fasten with the upright support rods. In the process of adjusting the level of the shelf of the rack, it is necessary to adjust the tapered tubes and the locating pieces. The adjustment of the tapered tubes and the locating pieces can not be easily carried out.